BBWC replacment - HOT?

[David Orwig]

Any concerns about replacing a failed BBWC battery while the server is up and running? 380 G4 has the remotely wired battery holder that battery clips into. It would seem that plugging a battery which already has a charge into a memory chip has it's own inherent risks.

I now open myself to many crazy posts from experts and self-proclaimed experts. I've been doing this type of work for many many years and obtaining downtime has gotten harder and harder (and harder).

[Michael A. McKenney]

I would not do it. I have never heard of a hot battery. I would get a full backup before changing it. It is best done with server down. removing the battery can cause write back to change to write through. It could affect array writes and you could lose data.

I would do it off.

[David Orwig]

I did find the following from the Maintenance and Service guide for the 380G4:

"To prevent a server malfunction or damage to the equipment, do not add or remove the battery pack while an array capacity expansion, RAID level migration, or stripe size migration is in progress."

The only way any expansion or migration can be performed is while it is powered on.

[David Orwig]

P.S. by hot, I meant hot swap (of the battery only). It does not require removal of the cache module.

[Torsten.]

Read carefully!


This note is written between step 3 and 4.


Did you notice step 1???

1. Power down the server.
...

[David Orwig]

How is a stripe size migration accomplished while the server is powered down?

[Torsten.]

This notice is in the non-hotplug chapter.

My understanding is you should not power down and replace while such operation is in progress.

[Torsten.]

David, this is IMHO also a reason why people want to boot from SAN - eleminate the array controller as an SPOF.

[Trygve Henriksen]

Array expansion, rebuilds and similar oerations are only postponed during a shutdown and will continue when power is restored.

As these operations are handled by the controller, not the OS, it's more likely that the cache contains valid data if the server is shut down during these operations.
Swapping out the battery will then clear the cache with potential data loss as a result.
(This part is a guess on my part... )

Maybe HP should have a line of controllers with DUAL hot-plug battery packs?
(For all I know they may already have them?)

[Nicolai Rasmussen]

If it's possible to disable the BBWC module, I don't see any reason why it shouldn't be possible to replace the battery while the server is powered on.

I haven't tried it though, but I've often thought about it myself...

Let me know how it goes! :D

[Torsten.]

Regardless if it works or not, it remains unsupported ...

[Troy Swope]

if the battery is already dead and needs replaced, what would the negative affects be?

[Mauricio Salas]

Well, technically, it could work, but in the process you can damage a server, so if you a spare server where you can practice, go ahead and let us know :) but wouldnt do it, really

[Christopher Seary]

The user guide for the Smart Array P400 Controller specifically warns against replacing the battery pack while the server is powered up:

http://h20000.www2.hp.com/bc/docs/support/SupportManual/c00572169/c00572169.pdf (see page 21)

The battery cable connector is not designed for hot swap; so there is a risk of electrical short and permanent hardware damage.

Too bad - with the BBWC already disabled there seemed little risk of data loss. But once you let the magic blue smoke out ...